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Wednesday, 2 February 2011

Some experts have warned that bribing children to eat healthy foods can be counter-productive, undermining their intrinsic motivation and actually increasing disliking. Lucy Cooke and colleagues have found no evidence for this in their new large-scale investigation of the issue. They conclude that rewards could be an effective way for parents to improve their children's diet. '...rewarding children for tasting an initially disliked food produced sustained increases in acceptance, with no negative effects on liking,' they said.

Over four hundred four- to six-year-olds tasted six vegetables, rated them for taste and then ranked them in order of liking. Whichever was their fourth-ranked choice became their target vegetable. Twelve times over the next two weeks, most of these children were presented with a small sample of their target vegetable and encouraged to eat it. Some of them were encouraged with the reward of a sticker, others with the reward of verbal praise, while the remainder received no reward (a mere exposure condition). A minority of the children formed a control group and didn't go through an intervention of any kind.

After the two-week period, all the intervention children showed equal increases in their liking of their target vegetable compared with the control children. However, when given the chance to eat as much of it as they wanted (knowing there was no chance of reward), the kids who had previously earned stickers chose to eat more than the kids who'd just been repeatedly exposed to the vegetable without reward.

At one- and three-month follow-up, the intervention children's increased liking of their target vegetable was sustained regardless of the specific condition they'd been in. However, in terms of increased consumption (when given the opportunity to eat their target vegetable, knowing no reward would be forthcoming), only the sticker and verbal praise children showed sustained increases.

So, how come previous studies have claimed that bribery can undermine children's intrinsic motivation, actually leading to increases in disliking of foods? Cooke and her colleagues think this may be because past lab studies have often targeted foods that children already rather liked. Consistent with this explanation, it's notable that past community studies that reported the successful use of rewards targeted unpopular vegetables just as this study did.

An important detail of the current study is that verbal praise was almost as effective as tangible reward. 'Social reward might be particularly valuable in the home,' the researchers said, 'because it may help parents avoid being accused of unfairness in offering incentives to a fussy child but not to the child's siblings.'
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